This is not about a "siege of Delft" (there was none at this time) but the book was printed in Delft. It shows a demonstration of the Dutch Guard how the slides of the artillery train were used at a siege as shields for an assault on the redoubts. Note that the colors of the uniform are slightly wrong as the yellow of the cuffs and gaitors was bright orange instead. Hence the misinterpretation as "Swedish" ;)